Engine Detonation & Pre-Ignition

今日溫書…繼續Engine先~ 睇一下上年差吾多時間既發文…再收集一下新野: 溫故知新~ 我要揸飛機 XDDD

有一句說話好真…書第一次讀係知…第二、三、四、五次讀先會識…以前我真係讀書…知道佢UP咩…但未識…今晚一個人安靜下…睇返之知自己入左誤區都吾知 >3<”

今晚就一文搞清楚某D Terms 既分別!

Reciprocating Engine v.s Turbine Engine

Reciprocating and turbine engines differ primarily in their mechanism for converting fuel energy into motion.

Reciprocating engines use pistons that move back and forth in cylinders, converting combustion pressure into rotational motion.

Turbine engines, on the other hand, use a continuous flow of hot, high-velocity gas to spin a turbine, which then drives a shaft.

Reciprocating Engine (Piston Engine) 可以用gasoline , 但都可以用 Diesel !

Reciprocating Engine (Piston Engine) 可以用gasoline , 但都可以用 Diesel ! (呢個concept 好好好好好重要!)

Example:

TB10 Tobago engine uses gasoline – 180-horsepower Lycoming O-360-A1AD piston engine

DA42 use jet (diesel) – Austro Engine AE300 (Austro Engine E4)

TB10 同 DA42 都係用piston engine…但分別就係前者用gasoline, 後者用jet (diesel)…感當然運作原理都吾同左~

下面條片就係PK 兩者

繼續搵記憶!

TB-10 typically equipped with a Lycoming O-320 engine. It has a four-cylinders. It is a naturally aspirated engine.

Gasoline 含意…有spark plug…行otto cycle ; 同埋有 carburetor

Intake Compress Power Exhaust

一向讀書都有教粗人記法: Suck, Squeeze, Bang, Blow

因為D valves 吾係真係exactly open or close at the Intake compress power exhaust stages

一講到就要記多3個名詞:

1. Valve Lead
2. Valve Lag
3. Valve Overlap

總之慨念就係要吸最多fuel-air mixture, 所以Intake stage(行內叫stroke) 就會有valve lead (open) and valve lag (to close)

要提早燒for maximum power … 所以又有spark (fire) before real power stroke

跟著又要設計到排走最多廢氣…所以就有valve lead (open) before real exhaust stroke and valve lag after real exhaust stroke

之餘想排更多廢氣走當然要用”新鮮”氣換…所以又有valve overlap when both intake valve and exhaust valve open.

不斷係到stroke stroke stroke 咩係stroke?

就是指個piston from top (top dead center) to the bottom (bottom dead center) 為之一個stroke.

如果你死記梗背一定背到…但會比人問到口啞啞…但理解左就一理通百理名…其實飛機就係感~ XDDD 加油!

好…跟著一講到piston engine…基本上就會比人問基本troubleshooting…咩係preigntion, 咩係detonation.

Concept 好簡單…preignition 有個pre 字…意味係precursor for detonation…同埋preignition 通常”社區感染” 但detonation 就真係爆到周圍都係

當然兩樣野好吾同… 皮detonation 就係爆炸…背書咁補就係 “Detonation is uncontrolled, explosive ignition of the fuel-air mixture.”

“Preignition occurs when fuel-air mixture ignites prior normal cycle.”

Detonation 係因為個cylinder 異常地熱..感當然有常見幾大原因:

1. Wrong fuel, more precisely, used lower grade of fuel with less anti-detonation capability
2. Extended climbing with low speed
3. Too lean of mixture

Preignition 原因主要都係spark plug fouling …deposit create hot spots

兩個主要症狀都係loss of engine power, 但detonation 通常會有埋  “Ping” 一聲

感點算? 盡快land…不過都有D野做到既:

1. Reduce Power
2. Mixture to Reacher
3. Cowl flaps open, if able
4. Shallow the climb, if you are climbing

Btw…下面條片雖然講車…但解釋得幾好…同埋都可以參考~

搞左成晚都仲未開始 Diesel cycle…睇黎要明晚再戰…仲要返工 XDDD