X-CGP-ClamAV-Result: CLEAN X-VirusScanner: Niversoft's CGPClamav Helper v1.23.0 (ClamAV engine v0.103.0) X-Junk-Score: 0 [] X-KAS-Score: 0 [] From: "Charlie England ceengland7@gmail.com" Received: from mail-oo1-f45.google.com ([209.85.161.45] verified) by logan.com (CommuniGate Pro SMTP 6.3.5) with ESMTPS id 154253 for flyrotary@lancaironline.net; Tue, 20 Jul 2021 17:03:40 -0400 Received-SPF: pass receiver=logan.com; client-ip=209.85.161.45; envelope-from=ceengland7@gmail.com Received: by mail-oo1-f45.google.com with SMTP id n187-20020a4a40c40000b029025e72bdf5d6so110004ooa.0 for ; Tue, 20 Jul 2021 14:03:41 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-language; bh=HHYXq/1ur0nE1kIuxDijlta/zxeOZueNpGnU/Xb8sWU=; b=bzlyW0xQht3nglJyKyJhIpPscs8T8TZcVQzyjnrgMpQbs95HjeLoBAd8wCKqGTLrQF LSNMrOgdxwVdYYHlXqu+LEXXpLxVwm4O5entayRBvBz6Y76RytP1bbcl9qbsLoH1cffg 7f/VDIN3FkULogjGFrqmKjmrDsVtyQvBr/iYwQF50pNfQwH/zaDMM1SskYXCOfi8lfdT VCd3AO28AgwvODShD8ejgYW+33ngBZtene0r1YgX9UT8g0AwXNv8lWwPYVmDRmsaAwDq Rb1lv0+uf9EZy6thPleBCTzVDQkPthqC4mA/qLyIbH0ZGxJxxdiH/LyGhVWovXyIgQp3 kZUg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language; bh=HHYXq/1ur0nE1kIuxDijlta/zxeOZueNpGnU/Xb8sWU=; b=Qas+SaNsks47OhuFpVc0mY9pN1Ub0B9v3+Hd2kyWvsykICVinbc03sV712sv5PDJGx p2iYo+8DjqZIp1Qll7Z0Uy82ZWtXJERG+xneI2s0/z3Um+lsEDF7vosinigVsttNfvEp f1aU8QwXR9skvOU19zA7iUAE4yjHXfdGBcvG2N6egkr0J4WM9meErKCrnTyaTYnhdULX lWWCjmMvvf9o08g5M1DwDaIPiI870VVYqjffsy5xzct7u1iUaG3NHa9RDC4HTcg9hQqx dNDRu31h112vhTFT7BfsJle8Y6WIqDMRfBFVqZHclKJfTxSZD/I7RhNP0zxSpol5IKYU 0Icw== X-Gm-Message-State: AOAM531GhsFCyz5f6cbWkVRMiOAUHDRsdMDCPxTPXpbz9gLf49BgGOxC n+sVqNBKmQ+5eSnXn9+NLKBUGtzoDxs= X-Google-Smtp-Source: ABdhPJxVfAVncWYX3lnpqzsh6smbR1idyfozpQ5Z/qHYgdbJfiSU5Cnnmntv8Ln8VQbIr/Sn4o8daQ== X-Received: by 2002:a4a:5850:: with SMTP id f77mr22307154oob.15.1626815003690; Tue, 20 Jul 2021 14:03:23 -0700 (PDT) Return-Path: Received: from [192.168.1.18] ([172.58.144.98]) by smtp.googlemail.com with ESMTPSA id o19sm4150078oov.36.2021.07.20.14.03.23 for (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 20 Jul 2021 14:03:23 -0700 (PDT) Subject: Re: [FlyRotary] Fwd: Inlet cooling article To: Rotary motors in aircraft References: Message-ID: Date: Tue, 20 Jul 2021 16:07:21 -0500 User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/alternative; boundary="------------FDFAB4A6A7876AA03C4D5176" Content-Language: en-US X-Antivirus: Avast (VPS 210720-4, 7/20/2021), Outbound message X-Antivirus-Status: Clean This is a multi-part message in MIME format. --------------FDFAB4A6A7876AA03C4D5176 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit On 7/20/2021 3:26 PM, Marc Wiese cardmarc@charter.net wrote: > Comments? > >> *Subject:* *Inlet cooling article* >> >>  https://www.kitplanes.com/down-to-earth-40/ >> >> >> Sent from my iPhone I remember the Laboda article about enlarging their cooling inlets, but not many of the details. This: The plenum receives air through two circular air intake ducts behind the propeller and squeezes it, Bernoulli-style, so that the air accelerates across the cylinders and between their fins, carrying the heat back, down and out an outflow "gate" at the back and bottom of the engine area, forward of the firewall. Is contrary to everything I've ever read about cooling efficiently. Faster relative flow will always have higher drag, all else being equal. Accelerating the air even faster than freestream just sounds crazy. My understanding is that there's a balancing act between having the room in an a/c to 'recover' (increase) differential pressure across the heat exchanger (engine fins, in this case), and causing too much drag from the air going through the fins too fast (there's aerodynamic drag in the heat exchanger, just like over the a/c itself). It's surprising to me that James made the plenum the way he did. The rest sounds like putting bandaids on stuff. The next-to-last image, of the final inlet, shows what appears to be a *much* smaller plenum inlet than the cowl ring in front of it, and a rather sharp edged lip where the plenum starts. It looks like the air would accelerate until it hits that sharp lip, and immediately go turbulent, which will kill any pressure recovery and actually slow flow into the cylinder fins. Most Lyc plenums I've seen (even the ones James made for the 4 cyl engines) have significant volume above the cylinders with smoothly expanding ducts feeding the plenum. That allows the air to slow in an organized fashion, which increases *pressure*, which is what actually makes the air move through the fins. But what do I know; I have an Economics degree.... Charlie -- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus --------------FDFAB4A6A7876AA03C4D5176 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: 8bit
On 7/20/2021 3:26 PM, Marc Wiese cardmarc@charter.net wrote:
Comments?

Subject: Inlet cooling article

I remember the Laboda article about enlarging their cooling inlets, but not many of the details.
This:
The plenum receives air through two circular air intake ducts behind the propeller and squeezes it, Bernoulli-style, so that the air accelerates across the cylinders and between their fins, carrying the heat back, down and out an outflow "gate" at the back and bottom of the engine area, forward of the firewall.

Is contrary to everything I've ever read about cooling efficiently. Faster relative flow will always have higher drag, all else being equal. Accelerating the air even faster than freestream just sounds crazy. My understanding is that there's a balancing act between having the room in an a/c to 'recover' (increase) differential pressure across the heat exchanger (engine fins, in this case), and causing too much drag from the air going through the fins too fast (there's aerodynamic drag in the heat exchanger, just like over the a/c itself). It's surprising to me that James made the plenum the way he did. The rest sounds like putting bandaids on stuff. The next-to-last image, of the final inlet, shows what appears to be a *much* smaller plenum inlet than the cowl ring in front of it, and a rather sharp edged lip where the plenum starts. It looks like the air would accelerate until it hits that sharp lip, and immediately go turbulent, which will kill any pressure recovery and actually slow flow into the cylinder fins.

Most Lyc plenums I've seen (even the ones James made for the 4 cyl engines) have significant volume above the cylinders with smoothly expanding ducts feeding the plenum. That allows the air to slow in an organized fashion, which increases *pressure*, which is what actually makes the air move through the fins.

But what do I know; I have an Economics degree....

Charlie

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