GIVE answer in 3 steps with explanation at the end of each step and final answer at the end2. An air tank with a nozzle has a pressure of 196.32 KPa and density of 1.9 Kg/m’. Outside the converging-
diverging nozzle, the pressure is atmospheric and designed to have a Mach No. of 1.0 and 1.5 at the throat
and exit respectively. The area at the throat is 0.11". Calculate the following (a) Temperature and speed of
sound at the tank. (b) Pressure, density, temperature and speed of sound a the throat. (c) Mass flow at the
exit.
Question:
GIVE answer in 3 steps with explanation at the end of each step and final answer at the end2. An air tank with a nozzle has a pressure of 196.32 KPa and density of 1.9 Kg/m’. Outside the converging-
diverging nozzle, the pressure is atmospheric and designed to have a Mach No. of 1.0 and 1.5 at the throat
and exit respectively. The area at the throat is 0.11". Calculate the following (a) Temperature and speed of
sound at the tank. (b) Pressure, density, temperature and speed of sound a the throat. (c) Mass flow at the
exit.
This is AI generated Response.
Asked by: amu
Created at: 2025-07-25 15:56:46
Final Answer:
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Let's solve the problem step by step, as requested.
---
### **Given Data:**
- Pressure in tank, \( P_0 = 196.32 \) kPa
- Density in tank, \( \rho_0 = 1.9 \) kg/m³
- At throat: Mach number, \( M^* = 1 \), Area \( A^* = 0.11 \) m²
- At exit: Mach number, \( M_e = 1.5 \), Pressure is atmospheric (\( P_e = 101.3 \) kPa, assuming standard atm)
- Gas: Air (\( R = 287 \) J/kg·K, \( \gamma = 1.4 \))
---
## **Step 1: Temperature and Speed of Sound at the Tank**
### **a) Temperature at the Tank (\(T_0\))**
Using the ideal gas law:
\[
P_0 = \rho_0 R T_0 \implies T_0 = \frac{P_0}{\rho_0 R}
\]
\[
T_0 = \frac{196320}{1.9 \times 287} = \frac{196320}{545.3} \approx 360 \text{ K}
\]
**Explanation:**
We used the ideal gas law to find the temperature in the tank.
### **b) Speed of Sound at the Tank (\(a_0\))**
\[
a_0 = \sqrt{\gamma R T_0}
\]
\[
a_0 = \sqrt{1.4 \times 287 \times 360} = \sqrt{1.4 \times 103320} = \sqrt{144648} \approx 380 \text{ m/s}
\]
**Explanation:**
We used the formula for the speed of sound in a perfect gas.
---
## **Step 2: Properties at the Throat (\(M^* = 1\))**
Use isentropic relations for \(M^* = 1\):
#### **a) Temperature at the Throat (\(T^*\))**
\[
\frac{T^*}{T_0} = \frac{1}{1 + \frac{\gamma-1}{2} M^{*2}}
\]
\[
= \frac{1}{1 + 0.2 \times 1^2} = \frac{1}{1.2} = 0.833
\]
\[
T^* = 0.833 \times 360 = 300 \text{ K}
\]
#### **b) Pressure at the Throat (\(P^*\))**
\[
\frac{P^*}{P_0} = \left( \frac{T^*}{T_0} \right)^{\frac{\gamma}{\gamma-1}}
\]
\[
= (0.833)^{3.5} \approx 0.529
\]
\[
P^* = 0.529 \times 196.32 = 103.8 \text{ kPa}
\]
#### **c) Density at the Throat (\(\rho^*\))**
\[
\frac{\rho^*}{\rho_0} = \left( \frac{T^*}{T_0} \right)^{\frac{1}{\gamma-1}}
\]
\[
= (0.833)^{2.5} \approx 0.624
\]
\[
\rho^* = 0.624 \times 1.9 = 1.19 \text{ kg/m}^3
\]
#### **d) Speed of Sound at the Throat (\(a^*\))**
\[
a^* = \sqrt{\gamma R T^*} = \sqrt{1.4 \times 287 \times 300} = \sqrt{1.4 \times 86100} = \sqrt{120540} \approx 347.3 \text{ m/s}
\]
**Explanation:**
We used isentropic flow relations for Mach 1 at the throat.
---
## **Step 3: Mass Flow at the Exit (\(M_e = 1.5\))**
First, let's check the properties at the exit.
### **a) Isentropic Relations at the Exit (\(M_e = 1.5\))**
\[
\frac{T_e}{T_0} = \frac{1}{1 + \frac{\gamma-1}{2} M_e^2} = \frac{1}{1 + 0.2 \times 2.25} = \frac{1}{1.45} = 0.690
\]
\[
T_e = 0.69 \times 360 = 248.4 \text{ K}
\]
\[
\frac{P_e}{P_0} = \left( \frac{T_e}{T_0} \right)^{\frac{\gamma}{\gamma-1}} = (0.69)^{3.5} \approx 0.273
\]
\[
P_e = 0.273 \times 196.32 = 53.6 \text{ kPa}
\]
\[
\frac{\rho_e}{\rho_0} = (0.69)^{2.5} \approx 0.379
\]
\[
\rho_e = 0.379 \times 1.9 = 0.72 \text{ kg/m}^3
\]
\[
a_e = \sqrt{\gamma R T_e} = \sqrt{1.4 \times 287 \times 248.4} \approx \sqrt{1.4 \times 71291} \approx \sqrt{99808} \approx 316 \text{ m/s}
\]
\[
u_e = M_e \cdot a_e = 1.5 \times 316 = 474 \text{ m/s}
\]
#### **Mass Flow Rate at the Throat (Choked Condition)**
\[
\dot{m} = \rho^* u^* A^*
\]
At throat, \( u^* = a^* = 347.3 \) m/s
\[
\dot{m} = 1.19 \times 347.3 \times 0.11 \approx 45.5 \text{ kg/s}
\]
**Explanation:**
We used isentropic relations and continuity to calculate exit and throat properties.
---
## **Final Answers (Summary):**
### **Step 1:**
- **Tank Temperature:** **360 K**
- **Tank Speed of Sound:** **380 m/s**
### **Step 2:**
- **Throat Pressure:** **103.8 kPa**
- **Throat Density:** **1.19 kg/m³**
- **Throat Temperature:** **300 K**
- **Throat Speed of Sound:** **347.3 m/s**
### **Step 3:**
- **Exit Mass Flow:** **45.5 kg/s**
- **Exit Pressure:** **53.6 kPa**
- **Exit Density:** **0.72 kg/m³**
- **Exit Temperature:** **248.4 K**
- **Exit Speed of Sound:** **316 m/s**
- **Exit Velocity:** **474 m/s**
Let me know if you want the full calculation for the exit area (using mass flow continuity)!
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