X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 29 Jan 2009 23:23:54 -0500 Message-ID: X-Original-Return-Path: Received: from wind.imbris.com ([216.18.130.7] verified) by logan.com (CommuniGate Pro SMTP 5.2.12) with ESMTPS id 3457810 for lml@lancaironline.net; Wed, 28 Jan 2009 20:07:17 -0500 Received-SPF: none receiver=logan.com; client-ip=216.18.130.7; envelope-from=brent@regandesigns.com Received: from [192.168.1.144] (207-170-226-178.static.twtelecom.net [207.170.226.178]) (authenticated bits=0) by wind.imbris.com (8.14.2/8.12.11.S) with ESMTP id n0T16Yc1053453 for ; Wed, 28 Jan 2009 17:06:39 -0800 (PST) (envelope-from brent@regandesigns.com) X-Original-Message-ID: <49810111.1060205@regandesigns.com> X-Original-Date: Wed, 28 Jan 2009 17:06:25 -0800 From: Brent Regan User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.2) Gecko/20040804 Netscape/7.2 (ax) X-Accept-Language: en-us, en MIME-Version: 1.0 X-Original-To: Lancair Mailing List Subject: Re: Alternative Power Plants Content-Type: multipart/alternative; boundary="------------030402030206070408000200" This is a multi-part message in MIME format. --------------030402030206070408000200 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Hello Greg, Thank you for posting the pictures of the 20B aircraft installation you are fabricating. Your pictures and my personal past experience compels me to offer some words of caution. First, let me say that I have no idea as the the degree and quality of the engineering that has gone into this project to date. I am operating on a worst case assumption so please discard comments concerning issues that you have already addressed. I hope to present these in a self evident fashion. Know that I have been involved in rotary engine development since the late '70s, that I was involved in developing and building a 12A engine that competed and won it's class in the 24 hours of Daytona endurance race, that I have previously developed high output rotary engines for aerospace applications, that I worked with Charlie Jones at Curtis Wright to help market their SCORE aircraft rotary engine to Cessna and Piper and that I seriously evaluated the Mazda R26B engine (4 rotor winning Le Mans in '91, see SAE paper #920309) for my Lancair IV-P but opted to adapt a Lycoming TIO540. I flew that airplane, and won, the Denver to Oshkosh race in 1996. I now have over 1,000 hours on the original engine, including cylinders, pistons, rings and valves. The Wankel rotary engine we know is actually a compromise from Felix Wankel's original concept. The progenitor engine, designated DKM-54, featured a rotating rotor and housing arraigned such that each had a pure rotary motion. It was NSU's engineer Walter Froede that came up with the internally geared epicyclic design we are familiar with today. While this design is attractive due to its high power density and minimal parts count, it is not without its problems. One of the greatest problems is the high aspect ratio of the combustion volume. This leads to high percentage of charge quench and therefore poor brake specific fuel economy, high hydrocarbon emissions and high exhaust gas temperature. The CW SCORE engines attempted to overcome these shortcomings with a heavy fuel direct injection with spark assist. They were moderately successful. Another problem is the high power density with respect to heat rejection. Nominally 20 percent of the total combustion energy must be rejected to the cooling system. For a 300 Hp engine this heat flux is more than 100 kW, enough to run 20+ average single family homes. This is divided between the oil and coolant so the oil is at risk of chemical breakdown above 240F (natural oils). I solved this problem on the race engines by adding a tube shell intercooler between the oil and water cooling systems that limited the oil temperature to 230F by allowing the coolant to boil in the heat exchanger, dramatically raising the heat transfer rates. In short, your three biggest problems will be heat, heat and heat. Comments referencing your photos and subsequent post: 1) Belly mounted cooling system. The engine is VERY sensitive to air in the coolant. You MUST have a de-aeration system mounted above the highest point of the engine. This is a convenient point to place a "radiator cap". 2) Oil sump. It appears that you are using a stock oil sump configuration. You will find this insufficient for the anticipated continuos power levels. You need a high volume (12 Qt) remote tank dry sump system. The oil tank should have a centrifugal de-aeration design with multiple baffles. You should use a synthetic oil that is more tolerant to high temperature operation. 3) PSRU. It appears that you are using a planetary gear reduction, likely adapted from an automotive automatic transmission. Be advised that this configuration will generate between 1% and 2% of the transmitted power in heat, or about 5Kw at 300 Hp. You need a separate oil circulation and cooling system for this reduction. Prior attempts to use engine oil have been marginally successful, at best. I am also assuming that you have sufficient torsion compliance between the engine and gears to prevent cyclical load fatigue failure. 4) Induction Plenum. It appears you are planning single port injection based on mass flow into the intake plenum. It is important that the flow distribution of the plenum be tested, otherwise you may have poor charge and mixture uniformity across the three rotors. Flow testing can be accomplished with a shop vac and carburetor flow gage (balance). 5) Trochoid Cooling. Stock rotor housings have poor cooling distribution for high continuos power outputs. You need to have modified rotor housings and a high output water pump that is driven at the optimal speed. 6) High EGT. While having individual exhaust manifolds to the turbo, to utilize the kinetic energy of the exhaust, is good, these should be fabricated from Inconel to survive the high EGTs without failure. Likewise, the turbo needs to be a high temperature version. 7) Engine Mount. It is not apparent why the engine mounts are vertical. Thrust loads from the propeller can approach 1,000 lbs. The mounts, as designed, will not respond well to these loads. 8) PSRU mount. While I can appreciate that a heavy flat plate is easy to fabricate, it is poorly suited to react the gyroscopic precession loads and moments generated by the propeller. You would be wise to perform an independent engineering analysis of this design. 9) Transverse Engine Mount Triangulation. It is not clear from the photos but it seems like there is insufficient bracing to react transverse nose gear loads. Ask Skip Slater about this one. 10) Reversed slip couplings. The exhaust slip couplings seem to be reversed. Upstream should be the interior tube. The above list is by no means comprehensive. It is simply a free association exercise based on the posted photos. Engine installation design is serious business. There is a long list of designers that have died behind their engines. Success is in no small part dependent on the ability to understand and allow for the errors of those who have gone before. Remember that almost any engine can power an aircraft. The quality of the engineering and implementation of the installation determines the longevity of the application and, sadly, frequently the pilot. Fly safe. Brent Regan --------------030402030206070408000200 Content-Type: text/html; charset=us-ascii Content-Transfer-Encoding: 7bit Hello Greg,

Thank you for posting the pictures of the 20B aircraft installation you are fabricating. Your pictures and my personal past experience compels me to offer some words of caution.  First, let me say that I have no idea as the the degree and quality of the engineering that has gone into this project to date. I am operating on a worst case assumption so please discard comments concerning issues that you have already addressed. I hope to present these in a self evident fashion. Know that I have been involved in rotary engine development since the late '70s, that I was involved in developing and building a 12A engine that competed and won it's class in the 24 hours of Daytona endurance race,  that I have previously developed high output rotary engines for aerospace applications, that I worked with Charlie Jones at Curtis Wright to help market their SCORE aircraft rotary engine to Cessna and Piper and that I seriously evaluated the Mazda R26B engine (4 rotor winning Le Mans in '91, see SAE paper #920309) for my Lancair IV-P but opted to adapt a Lycoming TIO540.  I flew that airplane, and won, the Denver to Oshkosh race in 1996.  I now have over 1,000 hours on the original engine, including cylinders, pistons, rings and valves.

The Wankel rotary engine we know is actually a compromise from Felix Wankel's original concept. The progenitor engine, designated DKM-54, featured a rotating rotor and housing arraigned such that each had a pure rotary  motion. It was NSU's engineer Walter Froede that came up with the internally geared epicyclic design we are familiar with today.  While this design is attractive due to its high power density and  minimal parts count, it is not without its problems.  One of the greatest problems is the high aspect ratio of the combustion volume. This leads to high percentage of charge quench and therefore poor brake specific fuel economy, high hydrocarbon emissions and high exhaust gas temperature.  The CW SCORE engines attempted to overcome these shortcomings with a heavy fuel direct injection with spark assist. They were moderately successful.

Another problem is the high power density with respect to heat rejection. Nominally 20 percent of the total combustion energy must be rejected to the cooling system. For a 300 Hp engine this heat  flux is more than 100 kW, enough to run 20+ average single family homes. This is divided between the oil and coolant so the oil is at risk of chemical breakdown above 240F (natural oils). I solved this problem on the race engines by adding a tube shell intercooler between the oil and water cooling systems that limited the oil temperature to 230F by allowing the coolant to boil in the heat exchanger, dramatically raising the heat transfer rates. In short, your three biggest problems will be heat, heat and heat.

Comments referencing your photos and subsequent post:

1) Belly mounted cooling system. The engine is VERY sensitive to air in the coolant. You MUST have a de-aeration system mounted above the highest point of the engine. This is a convenient point to place a "radiator cap".

2) Oil sump. It appears that you are using a stock oil sump configuration. You will find this insufficient for the anticipated continuos power levels. You need a high volume (12 Qt) remote tank  dry sump system. The oil tank should have a centrifugal de-aeration design with multiple baffles. You should use a synthetic oil that is more tolerant to high temperature operation.

3) PSRU. It appears that you are using a planetary gear reduction, likely adapted from an automotive automatic transmission. Be advised that this configuration will generate between 1% and 2% of the transmitted power in heat, or about 5Kw at 300 Hp. You need a separate oil circulation and cooling system for this reduction. Prior attempts to use engine oil have been marginally successful, at best. I am also assuming that you have sufficient torsion compliance between the engine and gears to prevent cyclical load fatigue failure.

4) Induction Plenum. It appears you are planning single port injection based on mass flow into the intake plenum. It is important that the flow distribution of the plenum be tested, otherwise you may have poor charge and mixture uniformity across the three rotors. Flow testing can be accomplished with a shop vac and carburetor flow gage (balance).

5)  Trochoid Cooling. Stock rotor housings  have poor cooling distribution for high continuos power outputs.  You need to have modified rotor housings and a high output  water pump that is driven at the optimal speed.

6) High EGT. While having individual exhaust  manifolds to the turbo, to utilize the kinetic energy of the exhaust, is good, these should be fabricated from Inconel to survive the high EGTs without failure. Likewise, the turbo needs to be a high temperature version.

7) Engine Mount. It is not apparent why the engine mounts are vertical. Thrust loads from the propeller can approach 1,000 lbs. The mounts, as designed, will not respond well to these loads.

8) PSRU mount. While I can appreciate that a heavy flat plate is easy to fabricate, it is poorly suited to react the gyroscopic precession loads and moments generated by the propeller.  You would be wise to perform an independent engineering analysis of this design.

9) Transverse Engine Mount Triangulation.  It is not clear from the photos but it seems like there is insufficient  bracing to react transverse nose gear loads. Ask Skip Slater about this one.

10) Reversed slip couplings. The exhaust  slip couplings seem to be reversed. Upstream should be the interior tube.

The above list is by no means comprehensive. It is simply a free association exercise based on the posted photos. Engine installation design is serious business.  There is a long list of designers that have died behind their engines. Success is in no small part dependent on the ability to understand and allow for the errors of those who have gone before. Remember that almost any engine can power an aircraft. The quality of the engineering and implementation of the installation determines the longevity of the application and, sadly, frequently the pilot.

Fly safe.

Brent Regan




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