Description of the technical parameters of the turbine engine test bench

On the bench (Fig.1) is mounted turbo-shaft engine GTD 350 designed to work in a team driving the helicopter, PZL Mi-2, which consists of two these types of engines working in parallel. Power from the engine is transmitted to the rotor via a main  gearbox shared for both units. The tail rotor is also driven by the main gearbox via the intermediate and the rear gear. The main gearbox is also a relay of power for all units helicopter.

Fig.1. Scheme of a test bench of the GTD-350 turbo-shaft engine

Laboratory space is divided into two main parts:

• engine test house (Fig.2)
• pilot house (Fig.3)

In addition, the engine test bench includes:

• electrodynamic brake AMX 400/6000 (2000 Nm, 6000 rpm, 400 kW)
• brake cooling system with cooler CWT32 / 1200
• fuel tank of 600 dm³ (located in the yard)
• an air inlet,
• exhaust duct,
• engine oil cooling system,
• engine control system with the data acquisition system

Fig.2. Engine test house

Fig.3. Pilot house

In engine test bench situated on the ground we can obtain stationary characteristics of engine. However, on the basis of stationary characteristics we can also calculate characteristics referred to the aircraft engine fly conditions. In order to obtain a good engine performance during investigation conducted on the  test bench, many parameters is determined,  such as:

a)      load torque or braking torque -  M_TN;        

b)      rotational speed of driving shaft - n_TN;    

c)      power on the driving shaft (of power /free turbine) -  P_TN;    

d)      rotational speed of compressor- turbine shaft -  n_SP    

e)      inlet temperature of turbine -  T₃.     

f)      compression - π;      

g)      mass air flow rate - m_pow           

h)      mass fuel flow rate – m_p      

i)      thermal efficiency of engine –  h_c

One of a more important performance of turbo-shaft engine, from the point of view of optimizing the operating point of engine, is so called power/driving turbine rotational characteristic, which shows the relationship of parameters such as: power, torque, specific fuel consumption and exhaust gas temperature as a function of power turbine rotational speed for constant rotational speed of compressor- turbine shaft (Fig.4).

In Fig. 4 we can see that there is an optimal speed power turbine for which at constant speed compressor-turbine (n_SP = const) the maximum power turbine is obtained

Fig.4. Turbo-shaft engine speed performance of  power P_TN  as a function of  rotational speed  

of  power turbine  n_TN  for different rotational speed of compressor-turbine n_SP