1、第8章內燃機臺架性能實驗8-1 測量與計算參數一 測量參數1 轉速n 轉速傳感器2 油耗 油耗儀3 測功器讀數 測功器 4 各種溫度、壓力5 測量環境的溫度、濕度、壓力二 計算參數1實測有效扭矩 2 實測有效功率 （kW）式中：n轉速（r/min） Me實測有效扭矩（nm）3小時耗油量GT4耗油率ge=GT/Ne8-2 測試系統概述一、扭矩測試儀器臺架上都采用吸收式測功器，常用的有水力測功器、電力測功器、電渦流測功器。1）水力測功器水力測功器是一種典型的吸收型測功器，它將發動機的輸出功率轉變為熱量消耗掉，同時在此過程中完成轉矩測量。水力測功器主要有轉子和定子（外殼）兩部分組成。它的基本工作原理

2、是利用轉子在充滿水的定子中旋轉所產生的磨擦阻力來吸收發動機功率，同時通過與可擺動的外殼相連的測力機構測出轉矩。由于轉子的結構不同，水力測功器大體上分為柱銷式、盤式和渦流式3種型式。內燃機帶動測功機轉子旋轉, 將水攪向外圍, 水與攪棒的摩擦力帶動定子轉動。水環越厚, 摩擦阻力越大, 相當于外界阻力矩越大。優點：結構簡單、價廉、工作可靠、應用范圍廣、功率儲備大、使用方便；缺點：測量精度低、排水溫度不能太高、精度依賴供水壓力穩定性。2平衡式電力測功器其工作原理和普通發動機或電動機基本相同，可以將發動機的機械功利用發電機變為電能，也可用電動機把電能轉變為拖動發動機的機械能。電機的轉子和定子以磁通作為媒

3、介，轉子和定子之間的作用力和發作用力大小相等，方向相反。所以只要將其定子做成能自由擺動的浮動方式，便可應用與水力測功器一樣的測力機構或拉壓傳感器測出發動機轉矩。分直流電力測功器、交流電力測功器優點：負荷和轉速調節范圍廣、工作穩定、使用方便、運行經濟性好、吸收的能力可以利用，可以反拖發動機。缺點：設備費用昂貴、占地面積大。3電渦流測功器利用渦電流產生制動力矩而起制動作用。 由電渦流測功器結構圖可知，感應子主要由旋轉部分和擺動部分（電樞和勵磁線圈）組成。轉子軸上的感應子形狀猶如齒輪，與轉子同軸裝有一個直流勵磁線圈。當勵磁線圈組通以直流電流時，其周圍便有磁場存在，那么圍繞勵磁組就產生一閉合磁通。很明

4、顯，位于繞組左側的感應子具有一個極性，右側具有相反的極性。旋轉時，由于磁密值的周期性變化而產生渦流，此渦流產生的磁場同產生它的磁場相互作用，從而產生與被試機反向的制動力矩，使電樞擺動，通過電樞上的力臂，將制動力傳給測量裝置。DW系列電渦流測功器特性曲線表示測功器在不同轉速下所能吸收的功率范圍，它由OABCD組成。AB最大扭矩線，當最大扭矩為常數時所能吸收的最大功率，隨著轉速的增加而上升，在A點達到扭矩強度所能允許的最大功率。BC最大功率線。測功器達到最大扭矩點（A）后，隨著轉速的變化測功器所能允許吸收的最大功率。CD最高轉轉速線。測功器在工作時允許的最大轉速。 上述三段限線所包圍的區域為測功器

5、的工作范圍。凡動力機或機械設備的特性在OABCD所包圍的范圍內者均能用該型測功器進行特性試驗。用主戶在選用測功器時須留有余地。二、耗油量測試儀器可以分為容積式、質量式和重力式：以小野公司的油耗儀為例！Volumetric Flow DetectorsFour pistons are arranged radially in the flow detection unit, and move back and forth repeatedly according to the flow of fluid from the inlet to the outlet. The pistons are

6、rotated by the crankshaft, and their movement is transmitted to the magnetic-coupled rotation detection unit. The rotary encoder mounted on the rotation detection unit generates pulse signals in accordance with the amount of piston movement.Wide measurement range thanks to a flow rate ratio of 1:400

7、 or more Capable of compensating for errors caused by pulsating or backflow by means of a function for detecting the direction of rotationHigh reproducibility and high-speed response result in superb reliabilityCapable of simultaneous measurement of temperature and pressure during flow rate measurem

8、ent (FP-2240HA/2250A)Gravity Flow DetectorsIf the fluid level falls below L3, the pressure signal generated by the detector causes the solenoid valve V1 to open and more fluid to flow in. When the fluid level reaches L2, valve V1 closes. Measurement of the flow rate starts after the specified time f

9、or the surface of the fluid to reach the fixed level has elapsed. As the fluid level falls from L2 as it is being consumed, the output from the differential pressure transducer changes in accordance with the gravity of the consumed fluid, and the gravity flow rate is obtained from this changed amoun

10、t.Alarms are generated if the fluid reaches the L1 overflow level or falls to the L4 insufficient fluid level.High-accuracy flow rate measurement over a wide range Built-in air extractor function to counteract the mixing in of air bubblesAlarm function to warn of overflows and low fluid levels Densi

11、ty corrections due to changes in the temperature are no longer required.Increased pressure and pressure feed are available as options.Mass Flow DetectorsThe fluid that entered from the inlet passes through the tube and goes out through the outlet. With this flow meter, the application of its inheren

12、t vibration to the tube causes a movement equivalent to the angular velocity, thereby generating a Coriolis force. As shown in the figures above, since the tube for which the Coriolis force is being generated generates a twist proportional to the mass flow rate, the mass flow rate is calculated from

13、 the amount of this twist.Continuous measurement without being affected by temperature, pressure, or densityHigh measurement accuracy (up to a ratio of 40:1 within 0.1% of the reading accuracy)Density measurement enabledThe case provided with each detector is capable of purging internal air.其他：三、轉速測量五、測量方法一 速度特性 節氣門或油門開度固定不動，內燃機運轉，油溫、水溫達正常值。設定測定為速度特性測定，然后調整測功器負荷, 使轉速達到預定值, 測量計算GT、ge、Ne和Me，在特性曲線圖上標出該點。再調節測功器負荷，使轉速達