X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Thu, 29 Dec 2005 22:01:08 -0500 Message-ID: X-Original-Return-Path: Received: from imo-m26.mx.aol.com ([64.12.137.7] verified) by logan.com (CommuniGate Pro SMTP 5.0.5) with ESMTP id 905240 for lml@lancaironline.net; Thu, 29 Dec 2005 11:44:08 -0500 Received-SPF: pass receiver=logan.com; client-ip=64.12.137.7; envelope-from=REHBINC@aol.com Received: from REHBINC@aol.com by imo-m26.mx.aol.com (mail_out_v38_r6.3.) id q.11.5373e96d (18555) for ; Thu, 29 Dec 2005 11:43:19 -0500 (EST) From: REHBINC@aol.com X-Original-Message-ID: <11.5373e96d.30e56c27@aol.com> X-Original-Date: Thu, 29 Dec 2005 11:43:19 EST Subject: Re: [LML] Re: Where has all the power gone? X-Original-To: lml@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="-----------------------------1135874599" X-Mailer: 9.0 for Windows sub 5120 X-Spam-Flag: NO -------------------------------1135874599 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en George, That is an interesting concept. =20 But I don=E2=80=99t think it is even theoretically true. I think if you a= pply some=20 boundary condition analysis you will come to the same conclusion. On the contrary, theoretically it is true. It is first year thermodynamics. =20 The configuration you suggests does not appear to take into account the=20 effects of the connecting rod-crankshaft geometry. You are quite correct. I was refering to a theoretical perfect engine with=20 infinitely long connecting rods that doesn't suffer from these issues. Howev= er,=20 the effects to which you alude to have a negligable effect on the points I w= as=20 making. (actually, shortening the connecting rod moves the optimal theta PP=20 slightly closer to TDC in a real world engine as the piston accelerates fast= er=20 from TDC.) =20 =20 It is not the simple area under the expansion curve that results in the=20 power. It is the correct integration of the expanding pressure curve, with=20= the=20 contribution of each point on the curve a function of sin(theta-crankangle)= . I think you are considering torque here rather than energy or power. You nee= d=20 to factor the rotation of the crank shaft into your integral. Then you will=20 get the same result as the simple piston pressure/displacement annalysis. =20 It is not a desirable design to arrange the combustion event so that the=20 maximum pressure point in the combustion cycle gets multiplied by zero (0= =3Dsin=20 (zero degrees) in the integration of the pressure-expansion curve to arrive= at=20 the torque applied to the crank shaft. =20 In our perfect, theoretical world I'm not so sure I agree with you. In the=20 real world it is a different story. Here there are numerous issues, some of=20 which I alluded to in my previous post, that prevent us from achieving perfe= ction.=20 The two points I was trying to demonstrate were simply that 1) the optimal=20 theta PP is a moving target that is dependent on several factors, including=20= rpm=20 and 2) that theta PP is an indication of the inefficiency of the engine. Rob -------------------------------1135874599 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Content-Language: en

George,

That is an interesting concept.

But I don=E2=80=99t think it is even theoreti= cally true. I think if you apply some boundary condition analysi= s you will come to the same conclusion.

On the contrary, theoretically it is true. It is first year thermodynam= ics.

&n= bsp;

The configuration you suggests does not appea= r to take into account the effects of the connecting rod-crankshaft geometry= .

You are quite correct. I was refering to a theoretical perfect engine w= ith infinitely long connecting rods that doesn't suffer from these issues. H= owever, the effects to which you alude to have a negligable effect on t= he points I was making. (actually, shortening the connecting rod moves the o= ptimal theta PP slightly closer to TDC in a real world engine as the piston=20= accelerates faster from TDC.)

&n= bsp;

It is not the simple area under the expansion= curve that results in the power. It is the correct integration of the= expanding pressure curve, with the contribution of each point on the curve=20= a function of sin(theta-crankangle).

I think you are considering torque here rather than energy or power. Yo= u need to factor the rotation of the crank shaft into your integral. Then yo= u will get the same result as the simple piston pressure/displacement annaly= sis.

It is not a desirable design to arrange the combust= ion event so that the maximum pressure point in the combustion c= ycle gets multiplied by zero (0=3Dsin (zero degrees) in the inte= gration of the pressure-expansion curve to arrive at the torque applied to t= he crank shaft.

In our perfect, theoretical world I'm not so sure I agree with you. In&= nbsp;the real world it is a different story. Here there are numerous is= sues, some of which I alluded to in my previous post, that prevent us from a= chieving perfection.

The two points I was trying to demonstrate were simply that 1) the= optimal theta PP is a moving target that is dependent on several factors, i= ncluding rpm and 2) that theta PP is an indication of the ineffici= ency of the engine.

Rob

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